Chemical Exfoliation of graphene and other 2D-materials

UoM administered thesis: Master of Philosophy

Authors:

Sukhraaj Johal

Abstract

Graphene has been described as a 'miracle material' and since its isolation in 2004 there have been thousands of reports of its exceptional properties and the wide range of applications it could be incorporated into.This thesis focuses on several topics; the first being the liquid exfoliation of graphite using 'surfactant' like 1 - pyrenesulfonic acid sodium salt (1-PSA), this dispersion was produced using the sonication method and it was found the single-layer yield was ~ 20%. A graphene paper was produced using this dispersion and a second was produced from sonication of graphite in N-Methyl-2-pyrrolidone (NMP). The second paper was produced as a reference as it has been well characterised in previous studies. X-ray Photoelectron Spectroscopy (XPS) was performed on both papers to check no graphene oxide or graphene derivative had been produced. It was found there was a ~ 14% residual of 1-PSA molecules present in the 1-PSA based paper, compared to ~ 8% residual NMP in the corresponding paper. The second topic covers the transfer of anodic bonding graphene samples in solution. This technique allows deposition of mostly single and few-layer graphene flakes onto a glass substrate. The transfer method we adopted was to use cellulose acetate butyrate (CAB) in ethyl acetate, which forms a film, encapsulating the flakes on the substrate. These films can then be dissolved in ethyl acetate. Although, we had promising results at the beginning of this study, it was concluded that the graphene flakes were embedded in the CAB films and the cellulose could not be removed. The third part shows preliminary results on the production of new 2D materials using the solvent based and 1-PSA based exfoliation methods. These show promising results as longer sonication times are proving successful in producing thinner flakes.